Sunday, January 25, 2015

If you are following this blog for a while you may have noticed I rarely ever post about Panasonic plasmas.

Customers often ask us if we can fix one or other TNPA board and we usually answer we do not work on Panasonic boards.

When talking to laymen and not service tech the next question is almost always "are they that bad?".

No, they are not. Or not much worse or much better than the others.

We just do not have the resources to repair the three major plasma TV manufacturers in the world.

Before that changes plasmas may become obsolete and I'd like to use that chance to give a clue on repairing a Panasonic TV.

A Panasonic TC-P42S30 was brought the other day in shop for repair.

Here's the label from the back and here's the TV look after you take the back cover off:

Failure symptoms: The symptom was as stated in the title: the TV would click on, produce no image and click off within a few seconds. It may have been giving an error code through a number of blinks on the power LED, but I did not pay attention to that.

Troubleshooting: Like most other plasma TVs Panasonics are know for failures in power supply boards and the sustain boards (of course some also fail in the main or elsewhere, but those are less).

The power board was clicking, which means it was getting standby power all right and the failure would have been on either the main power circuit (+5V main, +Vg (if present), Va, Vs etc.) or in a sustain board.

After a quick check on the fuses of the power as it was mounted on the TV and finding nothing we moved for a quick check on the power components of the Y sustain board (SC board in Panasonic terminology).

As you can see on the picture this is a combined sustain and output buffer board as is normal for some time now. The board in reference is TNPA5349:

We ran a quick check on the not-so-many SMD mounted power transistors and diodes and were not surprised to find a diode and a transistor that read short:

Those were the Q441 transistor DG302 and the D481 diode RF1501.

When we removed the transistor from the board the shortage over the diode disappeared and it read normal.

The DG302 transistor was the only failure on the board in this case and replacing it restored functionality of the set.

DG302 is popular choice in many Panasonic sets and is used both in its SMD and heat-sink mountable packaging.

1) If you are into electronics and doing things right I'd recommend you get TWO transistors and enhance the stock Panasonic build with TWO transistors working in parallel. There's plenty of space to solder another one there and you'd need to run a 5.6 ohm resistor from the gate to the point on the board just after the 5.6 ohm resistor of the original Q441 is.
You'd also need to run a wire from the third leg to the third leg of Q441.
Cutting the load in two this way you can rest assured this transistor is not going to fail you again.

2) There will be cases when this transistor won't be the only thing that has failed on the board.

3) Inserting the display FPCs into the SC output connectors has been a PITA for this set.
Do not affix the SC board in place with the screws- put one or two in, but let the board loose. That helps the insertion and still be extra careful to make sure you've plugged both ears evenly in the connector.

Tuesday, January 6, 2015

I don't usually write about TVs we don't offer a repair for here, but I am making an exception here.

First, we may actually start offering a repair service for the 6871QYH057B YSUS and 6871QZH060B ZSUS boards eventually (search at www.coppelltvrepair.com to find out) and second, the two boards are awfully close in design to the 50'' versions utilizing the same IPM modules, to which we are probably the single biggest service center in US, possibly after LG themselves.

Anyway, yesterday we got hauled in an LG 60PC1D 60'' plasma TV for repair. Fairly old, and even more heavy, but darn it, it's well done inside:

The complaint was a dark, blotchy image and unfortunately at the time I did not take a picture of the display.

The tech who brought it (we often get TVs by local TV repairmen, probably more often than we get TVs from end users locally) said the fuse on the ZSUS board blows as soon as the TV gets started.

Actually he also said he got a replacement board from Union Electronics, but it came with a blown fuse, so they exchanged it and the second one worked for 5 minutes and also blew the fuse.

That got me a little nervous because it meant the problem could have been elsewhere , e.g. in the plasma display controller, which could have been messing the signals and overheating or just crashing the IPMs on the ZSUS board. I've seen that in other TVs, although rarely.

Anyway, at the very least it was clear where to start, so I took the ZSUS board 6871QZH060B out and checked the IPMs. There were no shorts and the E versions were used from what I could tell (YPPD-J015E and YPPD-J016E since both were thin and only had 2 screws for the heat sinks meaning they weren't C or B versions).

In the 50'' models that we've done easily over a thousand of, when the E version is used the two most common failures are 1) failure in the J016E resulting in a particular shortage; and (remote second) failure in J015E almost always resulting in one of several possible shortages (e.g. Vs to GND or SUS_OUT to GND or Vs to SUS_OUT).

Well on this 6871QZH060B there were no shorts whatsoever.

But when I took out the SUS IPM here's what I found:

(for some reason Blogger insist on showing the picture in portrait mode; it shouldn't but I'll leave it as it is and you can mention Google favorably in an absent manner - maybe they'll get it eventually)

As you can see the SUS IPM has left a nice good proof of a failure on the board.

Since it could have been killed by a failed ER module, though, I did replace both. We always do.

Well almost always. A certain failure in the ER module alone can be treated by replacing the ER alone.

However a failure in the SUS module is best addressed by replacing both - that's what we've learned early in our experience with those and it has served us well.

After replacing both IPMs and the fuse (6.3A) we got this:

It worked that way for about 2 hours and then we delivered it back to the happy repairman.

We charged $120 for that and I am sure it ended up costing well over $200 to the customer.

Frankly I think it's fair if the guy had to order two boards, haul the TV to his shop and then to us and then back to his shop (where he'd be testing it longer) and eventually back to the customer.
Come to think about it..perhaps over $300.

Oh well...you know the old saying...the one with the idea gets a dollar, the one who implements it gets $10 and the one who sells it makes $100...so much for the great ideas :-)